How Much Is Too Much?

A testing lab is looking at water-usage in the three main filtration technologies

The International Association of Plumbing and Mechanical Officials is hard at work updating its Green Plumbing & Mechanical Code, a supplemental model code meant for adoption by states, cities or counties interested in establishing energy efficiency requirements.

But included among the usual proposals about pump, heater and
cover standards, is a look at pool and spa filtration —
particularly in residential pools — to explore water usage
and how filters can affect the energy consumption of a pool.

Here, professionals discuss the Green Code and its status, as
well as what the industry currently knows about how much water is
used by sand, cartridge and DE filters.

The concept

In its preliminary exploration, the IAPMO code-writing committee
has reviewed two studies on pools and water usage to better
understand filtration in residential applications.

But in doing so, it has become apparent that more information is
necessary — and that making generalizations about filtration
and water use is difficult. Not only are the needs of one pool, spa
and waterfeature different from the next, but even brands within
the same category of filter technology can vary.

In 2010, a study was prepared for the California Urban Water
Conservation Council that looked at the number of ways that water
is lost from pools, spas and waterfeatures, including evaporation,
leaks, splash-out and equipment operation. It referred to filter
backwashing as “one of the largest single uses of water by
pools and fountains.”

The research stated that cartridge filtration is the most
water-efficient for all but the largest pools, since it
doesn’t require backwashing. It also cited a study performed
by the National Resource Defense Council saying that, in
residential applications, properly sized cartridge systems use less
energy than comparable sand and DE units.

In the DE category, the study mostly focused on a type of filter
used almost exclusively in commercial applications —
regenerative DE filters — saying that these systems save
significant amounts of water and filter media. But this
didn’t apply to residential pools and spas.

The study put forth certain assumptions based on conversations
with pool professionals and homeowners. But it became clear that
broad-sweeping generalizations can’t be made when it comes to
filters and water use, because every situation is different.

“There’s no such thing as normal,” says Bill
Hoffman, an environmental engineer and president of H.W. Hoffman
& Associates in Austin, Texas. Hoffman’s company and
another firm were involved in compiling the study for the
CUWCC.

For instance, a pool is going to be backwashed more frequently
if it is used often and located in an area with a long swim season,
than if it were mostly for ornamental purposes and set in a colder
region.

For now, the group investigating water usage agrees that more
information is needed. “It’s our obligation to
determine that what’s being presented to us has
substantiation, and what was provided to us was a very small window
of information from one individual in one particular region of the
country,” says Dave Viola, Senior Director of Technical
Services for IAPMO.

They also say that industry input is crucial. “It’s
so important we get the good feedback of some real, honest-to-gosh
test data from the industry,” Hoffman says. To that end, the
Association of Pool and Spa Professionals is collecting information
from the industry that it will then supply to the task group.

At this point, Viola says, it isn’t known exactly how the
code will read. “It could [remain the same],” he says,
“or push for an industry standard for creating efficiency
requirements for filtration devices, or identifying technologies
that are preferred or that should be restricted based on their
energy and water consumption needs.”

The IAPMO Green Code is updated approximately every two years,
with the next version due in 2014. Viola doesn’t believe the
filter issue will be settled by then.

Technologies compared

Industry professionals agree on the face of it that sand filters
use more water in backwashing and cleaning than other types. But
there are a myriad of things to consider, they say, such as
disposal concerns, costs, space and plumbing requirements and
what’s best to clean the water.

Each type of filter is going to use water for backwashing and
cleaning, these professionals add. Even cartridge filters, which
don’t require backwashing, do have media that must be hosed
down, and just accessing the inside of the filter requires emptying the tank.

And a properly sized filter will not need frequent backwashing,
says Alison Osinski, president of Aquatic Consulting Services,
based in Avalon, Calif. Moreover, since sand actually benefits from
running a little dirty (because this helps the medium sift out
smaller particulates), that extends the time between cleanings even more.

In addition, each type of filtration has its own drawbacks. The
use of diatomaceous earth is highly regulated in certain areas
where the government is concerned about its dispoal, plus the DE
must be replaced with each backwashing or, as an alternative, taken apart and cleaned.

As far as cartridge filters, there is disagreement among the
industry about how much water they require for cleaning. Some claim
it can take a comparable amount to rinse the cartridge and drain
the tank as it would to backwash a sand filter, but others
haven’t experienced this.

It can take hundreds of gallons to clean a sand filter, says
Michael Orr, executive director of business development with the
Foundation for Pool & Spa Industry Education in Sacramento,
Calif., “Where with a cartridge, it takes usually less than
10 gallons of water to clean it. You could take it down to your
local do-it-yourself carwash and do it, if you used the proper
technique.”

He estimates that a maximum of 10 additional gallons would have
to be drained from the tank.

Others point to the fact that cartridge filters are rinsed with
clean city water. DE and sand filters, on the other hand, are
backwashed with pool water that could stand to be replaced anyway
to help reduce the total dissolved solids. Plus, the discarded
water doesn’t have to go to waste. “Everybody in
Phoenix will just backwash out into their lawns so they’re
not wasting it,” says Bill Rowley, a consultant and president
of Rowley International Inc. in Palos Verdes Estates, Calif.
“You can water the lawn with gray water.”

About health

Some professionals wonder if water usage should be a consideration
when looking at filtration or anything that affects water
quality.

“We’ve got this water-shortage issue, but we also
have a water-quality issue,” Osinski says.

Removing water from the system and replacing it regularly is
actually desirable because it aids in reducing total dissolved
solids and is a cheap and easy way to help clean the water, many
remarked.

“Using water is not necessarily a bad thing,”
Osinski says. “There are some situations where that’s
exactly what we want, because you need to get rid of some of that
water. They’re looking at one issue, which is water
conservation, but they’re forgetting this other issue, that
the water we’re swimming in develops a lot of problems and
needs to be changed.”

This is especially true in hot, dry climates where evaporation
occurs at high rates. When this happens, water leaves the pool but
solids don’t, resulting in a vessel that is more laden with
TDS than before. “If you live in Palm Springs, you’re
probably losing 8- to 12 feet of water each year due to
evaporation, but those solids are all staying behind,”
Osinski says. “It’s going to be pretty cruddy water if
you’re not diluting it.”

In the long run, these professionals believe, being able to
choose a filter that best meets the needs of the pool and its owner
will go the furthest toward saving water, because the filter that
keeps the water the cleanest will stretch the intervals between
pool drainings.

As for herself, Osinski says she would use sand for her home if
she had a pool, because it’s a less expensive alternative
that’s easier to clean and maintain. But she recognizes that
what’s best for her isn’t what’s best for others.
She and other professionals hope that IAPMO’s Swimming Pool
Task Group agrees with this in the end.

“If there was one filter that was the best, we’d all
be using it,” Osinski says.